THE EFFECT OF PEDAL CRANKARM LENGTH ON POWER PRODUCTION IN RECUMBENT CYCLE ERGOMETRY

Abstract

In human powered vehicles, adjustments in seat-to-pedal distance, seat tube angle, and body orientation (trunk angle with respect to the ground) will result in changes in hip, knee, and ankle angles. Changes in these joint angles often affect cycling performance by altering muscle length, moment arm length, angle of pull, joint range of motion, and/or the force/torque/power generated by different muscle groups. How changes in crankarm length affect joint kinematics and cycling performance has not been examined. Therefore, the purpose of this investigation was to determine the effect of changes in pedal crankarm length on joint kinematics and power production in recumbent cycle ergometry. Twenty healthy volunteer male subjects (mean age = 24.8 yrs, SD = 4.4 yrs) were tested in five pedal crankarm length (1 10, 145,180,230, and 265 mm) according to a randomized sequence (with a minimum of 24 hours rest between test sessions), using a free weight Monark bicycle ergometer (Model 814E). A variable seating apparatus was constructed and used, with the seat-to-pedal distance adjusted to 100% of each subject's leg length (as measured from the greater trochanter of the right leg to the ground). Pedal toe-clips were worn, and each subject's upper body was kept perpendicular to the ground. In each condition, the minimum and maximum hip, knee, and ankle angles were measured for one complete pedal revolution. A computerized 30 second Wingate anaerobic cycling test was used, with a resistance of 85 gm/kg of each subject's body mass (5.0 joules/pedal rev/kg BM). Peak power (5 sec) and mean power (30 sec) were determined by a SMI Power Program (Sports Medicine Industries). DM MANOVAs and post-hoc tests revealed that (1) hip, knee and ankle angles changed significantly with changes in crankarm length (p < .01); (2) peak power in the 110 and 145 mm crankarm lengths were significantly greater than that in the other lengths (p < .05); and (3) mean power in the 180 mm crankarrn length was significantly greater than that in the 1 10, 230 and 265 mm condition (p < .05). With increasing crankarm lengths, there is decrement in mean joint angles (hip, knee, and ankle), an increment in joint range of motion, a decrement in peak power, and a curvilinear end in mean power. Changes in pedal crankarm length by 35 mm will significantly alter joint kinematics to affect cycling performance, as evidenced by changes in peak and mean power. The shortest crankarrn length (1 10 mm) resulted in the largest peak power production (and fatigue index), whereas the middle crankarm length (180 mm) resulted in the largest mean power production. It was concluded that the optimal crankarm length to maximize performance in recumbent cycle ergometry will be dependent on the goal of the activity. - This research was supported by a grant from the UNLV Research Grants and Fellowship Committee.